The present invention relates to electromagnetic radomes and, more specifically, to wideband radomes for use at radio frequencies (RF) as well as microwave and millimeter-wave frequencies.
A radome is a structural enclosure that protects an antenna. Radomes are typically constructed of material that minimally attenuates the electromagnetic (EM) signal transmitted or received by the antenna. In other words, the radome is transparent to radar or radio waves. Radomes also protect the antenna surfaces from weather and conceal antenna electronic equipment from public view. Radomes can be constructed in several shapes (spherical, geodesic, planar, etc.) depending upon the particular application using various construction materials (fiberglass, PTFE-coated fabric, etc.). When provided on found on fixed-wing aircraft with forward-looking radar, radomes may be provided as nose cone sections of the fuselage.
A simple radome structure may be a uniform slab of material of thickness nλ/2 (where n is an integer) and λ=λvac/√(∈R).
Such radomes perform well at a single frequency, but are narrowband unless ∈R≈1 and fragile at millimeter-wave frequencies if n=1. Wideband performance typically requires a multilayer structure in which the dielectric constant and thickness of each layer are chosen to optimize performance. Examples of multilayer radome structures include, but are not limited to, A-sandwich structures where a low dielectric layer is sandwiched between two high dielectric layers and B-sandwich structures where a high dielectric layer is sandwiched between two low-dielectric layers.